The present invention relates to a structure of a battery receiving chamber of an electronic device to be worn on a human body and, particularly, to a structure of a battery receiving chamber for water-tightly receiving an air cell battery to which air has to be supplied.
A typical example of a conventional electronic device adapted to be used in a state attached directly to a human body is a hearing aid of the ear-piece type such as shown in FIG. 6. FIG. 6 is a side view of such a hearing aid 1, composed of a casing 2, a microphone 3 provided in an upper portion of the casing 2, electronic circuitry (not shown) including a signal amplifier and provided in the casing 2 for suitably amplifying sound picked-up by the microphone to provide a sound output, a curved sound conduit 4 in the form of a hook to be hanged fittingly on an upper portion of an ear of a wearer for conducting the sound output of the electronic circuitry through its top opening to the ear, and a battery (not shown) for energizing the amplifier. The battery is received in a battery receiving chamber provided in a lower portion of the casing 2, which is closed by a cover 5 as shown.
As shown in FIG. 6, a side face 2A of the casing 2 is shaped to fit the rear side of the ear of the wearer. With the curved sound conduit 4 and the side face 2A of the casing 2, the hearing aid 1 can be worn without giving any abnormal feeling to the wearer.
In order to make it possible to take a bath or to swim while protecting the hearing aid, in particular, the casing 2 thereof, against water, the hearing aid is usually made water-tight, otherwise, internal electric and electronic elements may be damaged.
Such water-tight structure is usually provided by utilizing O-rings of elastic material each in a junction of adjacent constitutional parts.
Such a conventional hearing aid is very effective insofar as the battery to be used is a shielded battery such as a mercury battery, etc.
On the other hand, an air cell, for example, an air-zinc battery, which utilizes oxygen in air to depolarize a positive electrode of the battery chemically by means of reduction of oxygen, is known as having less public pollution problems and a large electric capacity, compared with a conventional mercury battery. Therefore, it is highly desired to use such an air cell for a hearing aid. When such an air cell is to be used as the power source of the hearing aid, it is necessary to supply air to the battery. However, the water proof structure of the conventional hearing aid does not allow the use of an air cell since air can not be supplied to the battery provided within the casing thereof.